Process of enameling surfaces



UNITED ArnN'r rrrcn.

ANDREW- J. VOLLRATH, OF SI-IEBOYGAN, WISCONSIN.

PROCESS OF ENAMELING SURFACES.

SPECIFICATION forming part of Letters Patent No. 593,792, dated November 16, 1897.

I Application filed June 14:, 1897. Serial No. 640,766. (No specimens.)

To all whom it may concern:

Be it known that I, ANDREW J. VOLLRATH, a citizen of the United States, residing at Sheboygan, in the county of Sheboygan and State of W i sconsin, have invented a new and useful Improvement in Processes of Enameling Surfaces, of which the following is a specification.

My invention relates to an improved process of enameling the surfaces of any substances sufficiently refractory to withstand the usual muffle treatment. applicable to any article to which an enamel coating can be applied in the ordinary way, but its advantages will be found most pronounced in the case of large articles such as bath-tubs, sinks, stoves, and the like, to articles having uneven surfaces, caused by cameo or intaglio ornamentation-such, for ex ample, as radiator-loopsand to articles irregular in form and presenting ang1esas, for instance, bicycle-frames.

My improvement is confined to the operation of applying the enamel to the surface of the article preparatory to firing, all the remaining steps of the process being the usual onesthat is to say, the enamel employed may be of the ordinary composition or of any composition suited to the character of the article to be enameled, and the muffle treatment likewise is of the usual nature adapted to the requirements of the particular article. These matters are familiar to all skilled enamelers and require no further description.

Broadly stated, my improvement consists in mixing the enamel, ground to an impalpable powder, with a relatively large quantity of water, so that the mixture may flow With substantially or nearly the freedom of water, spraying the mixture upon the surface to be enameled, rapidly evaporating the water by the action of heat immediately upon its contact with the surface, whereby the enamel is left clinging thereto in a dry condition, and then firing.

The rapid evaporation of the water is best effected by heating the article before spraying it with the mixture, and in order to prevent rapid cooling of the article I find it advantageous also to heat the mixture. The process may be practiced by heating the-mix- My process isture alone, but if only one of the two is to be heated I prefer that it be the article. The heating may be repeated as often as required to permit coating of the whole surface to the desired thickness, or provision may be made for continuous heating.

Ihave obtained entirely satisfactory results by having the mixture at about boiling temperature and the article (cast-iron in this instance) at a temperature ranging from about 400 down to 200 Fahrenheit. I do not, however, restrict myself to any limits of temperature, except to say that the temperature must be high enough to cause rapid evaporation of the water, but not so high as to cause such a sudden and violent generation of steam as to blow off the enamel or cause blisters and other irregularities in the surface. To spray the mixture upon the article, an ordinary spraying or atomizing apparatus may be employed of a size suited to the requirements.

My process is applicable to every species of article capable of receiving an enamel coating, but it has its chief advantages in the case of such articles as cannot be satisfacto rily coated by the ordinary process of dipping. Wherever sharp edges or cavities exist the dipping process is impracticable, because uniformity of thickness in the coating cannot be obtained, and the dipping process has never been practically adapted to the coating of large and heavy articles. In the case of bath-tubs the dry process of enameling has been commonly practiced; but this is not only expensive, but very injurious to the workmen owing to the fact that the enamel has to be sifted upon the article while the latter is at substantially a fusing temperature. Owing to the difficulty and costliness of the dry process it is customary to enamel bath-tubs on the interior surface only, and comparatively few large articles are enameled. By my process, however, no difficulty is encountered in enameling the entire surface of a bath-tub, and this may be done with little additional expense and without the danger of warping that is always incident to re peated heating and cooling.

In enameling articles composed of material more or less absorbent in its nature-such as cast-iron, terra-cotta, brick, tiling, and the like-the ordinary wet process of coating is always attended with difficulties growing out of the fact that the article coated is liable to retain more or less of the absorbed moisture after the enamel has become dry. In the case of the more absorbent materials this is often sufiicient to cause blow-holes in the finished coating due to violent conversion of the moisture into steam under the intense heat of the muffle. This happens most frequently With the highly-absorbent materials, but it sometimes happens also in the case of cast-iron. \Vith this material, however, the principal obj ection is that the absorbed moisture tends to cause oxidation and produce discoloration in places.

One of the great advantages of my improvement is that it permits the coating to be applied not only with uniformity of thickness, but also with any degree of thickness that may be desired, depending upon the length of time for which the spraying is continued. It also admits of the use of various colors and shades of color upon the same article and the production thereby of endless varieties of ormentation, both in the Way of patterns, determined by stencils or otherwise, and of simple variegation.

\Vhen more than one coat of enamel is applied to an article, as in the case of a ground and a finishing coat, my process may be employed for each with or without successive firings.

Vhat I claim as new, and desire to soon re by Letters Patent, is

1. The process of onameling surfaccsm'hich consists in mixing enamel, ground to an impalpable powder, with Water to a state of high dilution, projecting the mixture in a fine spray upon the surface to be enameled, rapidly evaporating the Water, by the action of heat, immediately upon its contact With the surface, and then firing, substantially as described.

2. The process of enameling; surfaeespvhich consists in heating the article to a tempera- 

